Sepsis, or blood poisoning, is a potentially deadly medical condition characterized by a whole-body inflammatory state triggered by an infection. Sepsis is a vast clinical entity that takes many forms. The pathophysiology of a host response to infection is complex and the signs and symptoms of systemic inflammation may have an infectious or non-infectious etiology and are not specific. In response to microbes or viruses in the blood, urine, lungs, skin, or other tissues, the body may develop a systemic inflammatory response, eventually resulting in organ dysfunction and death. Patients with systemic infection are often difficult to distinguish from patients with similar clinical signs and laboratory findings without infection. Infection has multiple causes including that caused by bacterium, fungi, parasites and viruses.
Sepsis can be identified by the presence of pathogenic organisms in the bloodstream. Sepsis is usually treated with intravenous fluids and antibiotics. Sepsis can be the result of the presence of more than one type of organism, and there it is important to both identify the presence of the infection as early as possible before severe symptoms occur, and to regularly monitor blood samples from the patient during treatment to ensure the antibiotics are effective and the patient does not suffer from further infections.
Bacteriological evidence of infection may not develop at the same time as clinical signs of distress. Further, it requires time to grow a culture of organism from a blood sample to confirm the presence of infective bacteria and the results may be incorrect due to contamination, etc. As used herein, severe infection may include a diagnosis of sepsis, severe sepsis, septicaemia, and septic shock as well as disseminated intravascular coagulation (“DIC”). Also included in the definition of infection is systemic inflammatory response syndrome “SIRS” although it may have infectious as well as non-infectious origin (both of which are encompassed herein). SIRS may exhibit or develop into systemic inflammation that ultimately leads to multiple organ dysfunction syndrome. Patients with SIRS may develop the syndrome from infection, trauma, bums, pancreatitis, etc.
As used herein hemostatic dysfunction may be defined as an error in coagulation. For both DIC and sepsis, there is increasing recognition of common and overlapping pathophysiological pathways that link inflammation and coagulation. The recent therapeutic success of recombinant human activated protein C (APC) in severe sepsis especially after a myriad of unsuccessful strategies would support this further. APC suppresses thrombin generation via the inactivation of coagulation co-factors, Va and VIIIa and is also thought to have anti-inflammatory properties.
There is a continuing need to find early indicators or markers of infection, SIRS and hemostatic dysfunction due to lack of specificity of current methods of diagnosis. An early diagnosis may greatly increase recovery of the patient and reduce the morbidity and mortality rates associated with this population. Further a diagnostic marker or test to monitor the efficacy of treatment of the host response to infection, SIRS and hemostatic dysfunction is needed as well.
The time dependent measurement profiles of coagulation screening assays have been associated with predicting congenital, acquired imbalances and hemostatic dysfunction as described in Givens et al. WO 96/41291 and Toh et al. WO 00/46603. Once such profile is that of an activated partial thromboplastin time (“APTT”) assay having a decrease in plasma light transmittance before clot formation, now commonly referred to as a biphasic waveform (also referred to herein as BPW). This BPW has been associated with critically ill patients having DIC which is common in many primary diseases including sepsis. The biphasic waveform on coagulation instruments offers a simple and rapid test for early diagnosis of hemostatic dysfunction, including DIC.
As described in WO 01/96864 (Dec. 20, 2001), a calcium-dependent complex between C reactive protein (CRP) and lipoprotein (particularly very low density lipoprotein (VLDL)) has been identified as the molecular mechanism underlying the biphasic waveform. The complex may be used to identify patients with sepsis, SIRS and septicaemia in addition to patients with other hemostatic dysfunction that can lead to bleeding or thrombosis including DIC. Further, WO 01/96864 describes detecting the complex by a clotting assay, latex agglutination or gold sol assay, and immunoassay whereby the precipitate is formed prior to or in the absence of clot formation, depending on the reagent used.
While the biphasic waveform and the CRP-lipoprotein complex provide advances in the early diagnosis of different kinds of severe infection and haemostatic dysfunction (including DIC and sepsis), there is a continued need to simplify the assays further, and therefore a simple point of care version of the assay which can be carried out using a small amount of blood and gives an immediate read out is highly desirable.